Aqueous polyurethane dispersions for artificial leather applications

Abstract

Aqueous polyurethane dispersions are useful for making artificial leather and similar products. The dispersions contain polyurethane-urea particles dispersed in an aqueous phase. The particles are made using isophorone diisocyanate, certain cyclic amine chain extenders and certain polyol mixtures.

What is claimed is: 
     
       1. An aqueous polyurethane dispersion comprising a liquid aqueous phase containing an external surfactant and dispersed nonionic polyurethane particles, and containing no more than 0.5% by weight of organic compounds having a boiling point of less than 100° C. wherein the dispersed polyurethane particles are a reaction product of a nonionic polyurethane prepolymer and a diamine chain extender that contains a cycloaliphatic or aromatic ring structure, wherein the polyurethane prepolymer is a reaction product of an excess of isophorone diisocyanate with a polyol mixture, the polyol mixture including i) at least one random and/or block copolymer of propylene oxide and ethylene oxide having a hydroxyl functionality of 2 to 3, a hydroxyl equivalent weight of 200 to 6000 and an oxyethylene content of 2 to 89% by weight of the copolymer, ii) at least one poly(ethylene oxide) monol or polyol having a molecular weight of 200 to 12,000, optionally 10 to 65 weight percent, based on the weight of the polyol mixture, of iii) at least one polypropylene oxide) or random and/or block copolymer of propylene oxide and ethylene oxide that contain less than 2% oxyethylene units based on the weight of the block copolymer, iv) optionally one or more chain extenders having hydroxyl equivalent weights of less than 175 and exactly 2 hydroxyl groups per molecule and optionally v) one or more crosslinkers having three or more hydroxyl groups and a hydroxyl equivalent weight of less than 175, wherein i), ii), iii) when present, iv) when present and v) when present together constitute at least 95% of the weight of the polyol mixture and iv) when present and v) when present together constitute no more than 5% of the weight of the polyol mixture, and wherein the polyurethane prepolymer has an isocyanate content of 1 to 15% by weight of the prepolymer and a oxyethylene content of 1.5 to 20% by weight of the prepolymer. 
     
     
       2. The aqueous dispersion of  claim 1  wherein the diamine chain extender is piperazine. 
     
     
       3. The aqueous dispersion of  claim 1  wherein copolymer of i) has an oxyethylene content of 5 to 30% by weight of the copolymer and a hydroxyl equivalent weight of 500 to 3000. 
     
     
       4. The aqueous dispersion of  claim 1  wherein the poly(ethylene oxide) monol or polyol of ii) has a hydroxyl equivalent weight of 500 to 3000. 
     
     
       5. The aqueous dispersion of  claim 1  wherein the prepolymer has an isocyanate content of 2 to 8% by weight. 
     
     
       6. The aqueous dispersion of  claim 1  wherein the polyol mixture has an average hydroxyl functionality of 1.5 to 2.5 and an oxyethylene content of 3 to 6% by weight. 
     
     
       7. An artificial leather comprising at least one polyurethane layer formed by coagulating an aqueous polyurethane dispersion of  claim 1 . 
     
     
       8. A substrate having a coating layer, the coating layer comprising at least one polyurethane layer formed by coagulating an aqueous polyurethane dispersion of  claim 1 . 
     
     
       9. The aqueous polyurethane dispersion of  claim 1  wherein i), ii) and iii) when present constitute 100% of the weight of the polyol mixture.